You might want to contact this group (they also have a Facebook page):
https://www.myiag.org/
The Greenville bus system is called Greenlink, and the Spartanburg system is called Sparta:
Greenlink Transit | Greenville, SC - Official Website
https://www.cityofspartanburg.org/sparta
The commute between Greenville and Spartanburg is via I-85 and I-385, and that's a commute I wouldn't want to make every day. There are a lot of bad drivers in the upstate and accidents at rush hour on those roads are frequent.
Regarding safety: I don't know Spartanburg, but a high percentage of the crime in Greenville happens west and south of the downtown area. My recommendation is to look at the crime statistics here on the city pages for your current community with Greenville and Spartanburg and see how they compare. Most violence that happens here is drug related, and between people who know each other.